The present invention relates to a centrifuge having a centrifugal drum. The drum includes a drum bottom part, a centrifuge chamber bottom, a drum cover and a piston valve. The piston valve is axially movably disposed in the drum bottom part and is held by springs supported at the drum bottom part in a closed position. The piston valve is configured to open and close solid-matter discharge openings provided in the jacket area of the drum bottom part. The piston valve is movable by a control medium, which can be introduced into an opening chamber arranged between the piston valve, on one side, and a centrifuge chamber bottom, on the another side. The control medium acts against the effect of the springs premixing the piston valve to move into a position to open the solid-matter discharge openings.
Centrifuges or separators of the above-mentioned type are basically known. Reference is made here, for example, to U.S. Patent Document U.S. Pat. No. 4,164,317 as well as to German Patent Document DE 30 09 669.
For hygienic reasons, springs made of stainless materials are used in the case of the centrifuges or separators of the above-mentioned type.
By using springs made of a stainless material, a relatively large space is required for the accommodation of the springs. That is because springs made of stainless materials, in comparison to springs made of, for instance, unalloyed spring steel, require considerably larger dimensions to achieve the same forces.
An aspect of the present invention is a centrifuge of the above-mentioned type having only a relatively small space required for housing the springs.
According to the present invention, springs are made of an unalloyed spring steel and are encapsulated by sleeves made of a corrosion-resistant material. On one side, the springs project into a piston valve and, on another side, the springs project into bores of a bottom area of a drum bottom part.
By this comparatively simple and cost-effective construction, on the one hand, a high closing force is achieved and, on the other hand, a large piston valve stroke is achieved while the space for accommodating the springs is minimal. At the same time, a perfect insulation of each spring chamber with respect to a sterile chamber of the centrifuge is ensured.
Also an abrasion by friction under centrifugal force as well as corrosion influences upon the product being centrifuged are avoided.
These and other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings. dr
FIG. 1 is a sectional view of a centrifuge according to the principles of the present invention.
FIG. 2 is an enlarged view of a portion of the centrifuge of FIG. 1.